The present invention relates to a polishing method, an abrasive material, and a polishing apparatus, and particularly to a polishing method for polishing a surface of a member to be polished using an abrasive wheel holding fixed abrasive grains while supplying free abrasive grains to the surface of the member to be polished, an abrasive material used for the polishing method, and a polishing apparatus used for the polishing method.
A process of fabricating semiconductor devices includes a step of planarizing a wafer surface by lapping or polishing. For example, as shown in FIG. 1A, an interconnection pattern 2 made from aluminum is formed on a semiconductor wafer 1 made from silicon or the like, being covered with an insulating film 3 made from SiO.sub.2 or the like, and before formation of a multi-layered interconnection, the insulating film 3 is planarized for improving an accuracy and a coverage of the upper layer pattern.
In such a planarizing step, there has been adopted a polishing method using free abrasive grains. This method is characterized by polishing a wafer surface with an abrasive cloth (pad) while supplying a polishing solution (slurry) mixed with free abrasive grains. Such a polishing method using free abrasive grains, however, fails to obtain a sufficient flatness, more specifically, allows steps to remain on the surface as shown in FIG. 1B. The reason for this is as follows: namely, the pad must be made soft somewhat for uniformly polishing the entire wafer surface and enhancing the quality of a polished surface, and accordingly, such a soft pad is elastically deformed along steps of the wafer surface during polishing, thus failing to sufficiently remove the steps of the wafer surface.
For applications other than the above-described process of fabricating semiconductor devices, there has been adopted a polishing method using fixed abrasive grains separately from the above-described polishing method using free abrasive grains. This method is characterized by using an abrasive wheel in which abrasive grains are fixed with a binder, wherein polishing is performed by bringing the rotating abrasive wheel in press-contact with a surface of a member to be polished, and sliding such an abrasive wheel on the surface of the member to be polished. The abrasive wheel is composed of a binder; abrasive grains (fixed abrasive grains) which are fixed with the binder and which contribute to polishing; and spaces (pores) for temporarily holding slipped-off abrasive grains and/or chips, thereby treating the slipped-off abrasive grains in such a manner as not to be in contact with the surface to be polished and preventing occurrence of scratches on the surface to be polished. In the polishing method using fixed abrasive grains, a sufficient flatness can be obtained because of a large grinding characteristic of the method; however, the polishing tool having a high hardness may give rise to a large number of scratches on the surface to be polished. This results in degradation of surface characteristics (micro-scratch, metal contamination, and other surface state due to foreign matters). Another disadvantage is that since pores of the abrasive wheel are blocked by accumulation of fine abrasive grains slipped off and/or chips during polishing, the processing efficiency is lowered, and in order to eliminate the lowering of the processing efficiency, maintenance must be frequently performed for removing blocking of the pores of the abrasive wheel and setting the pores thereof.